This article addresses special issues in the design and use of printed circuit boards as they apply to power amplifiers, especially those operating in Class B. All power amplifiers contain power amplification stages themselves and associated control and protection circuitry. Most amplifiers also have a small-signal low-pass stage, balanced output amplifiers, a subsonic filter, output meters, etc.

Other issues related to PCB design are also considered, such as grounding, safety issues, reliability, etc. The performance of a low-frequency power amplifier depends on a large number of factors, in all cases careful design of the printed circuit board is decisive, primarily due to for the danger of distortion caused by inductive interference; Possible interactions between signal paths and power rails can very easily limit the amplifier's linearity, so it is difficult to overestimate the importance of this problem. The selected circuit board layout (component placement and trace pattern) will largely determine both the distortion and crosstalk levels of the amplifier.

In addition to the above considerations regarding amplifier performance, the circuit board design will have a significant impact on manufacturability, ease of inspection, repairability, and reliability. All of the above aspects of the problem are discussed below.

Successfully designing an amplifier PCB circuit requires a level of electronics knowledge to understand the intricacies of the effects described below so that the PCB design process runs smoothly and efficiently. It is already considered common practice when designing printed circuit boards for various fields of electronics to be left at the mercy of professionals who, while very knowledgeable in the intricacies of working with computer-aided design systems, have a very vague or even complete lack of understanding of the intricacies of how electronic circuits work. For some areas this approach may be acceptable; When designing a power amplifier, it is completely inadequate due to the fact that basic characteristics such as crosstalk and distortion level are highly dependent on the wiring diagram. A little further down, the PCB designer will be able to understand what we are actually talking about.

Crosstalk

Crosstalk (or the phenomenon of signal “flowing” from one channel to another, electrical interference caused by the passage of a signal in adjacent wires) is characterized, first of all, by the signal source (which can be any complex impedance) and the receiver, which usually has a higher complex impedance value , or the potential of a virtual, “floating” earth. When crosstalk in communication channels is discussed, typically the transmitting and receiving channels are referred to as voice and non-voice channels, respectively.

Crosstalk occurs and manifests itself in different forms:

1. Capacitive crosstalk results from the proximity of two electrical conductors in space and can be represented by using a virtual (or effective) capacitor connecting the two circuits. The capacitance of such a capacitor increases with increasing frequency in proportion to the value of 6 dB/octave, although higher rates of increase in capacitance are possible. Shielding the conductors with any conductive material completely solves the problem, although increasing the distance between such conductors turns out to be a less expensive method.
2. Resistive crosstalk occurs for the simple reason that the resistance of the ground bars is different from zero. Copper at room temperature is not a superconductor. Resistive crosstalk is independent of frequency.
3. Inductive crosstalk is rarely a problem in audio design; they can occur when two low-frequency transformers are recklessly installed too close to each other, but other than this case the problem can usually be forgotten. A significant exception to this rule is the low-frequency Class B power amplifier, in which the currents flowing through the power rails are half-sine waves and which can seriously affect the amplifier's distortion level if they are allowed to interact with the input signal circuits, the feedback loop, or the output circuits. cascade.

In most linear low-frequency circuits, the primary cause of crosstalk is unwanted capacitive coupling between the various circuits of the circuit, and in the vast majority of cases this is determined by the pattern of the wires and traces on the printed circuit board. In contrast, Class B power amplifiers suffer little or even negligible crosstalk caused by capacitive effects, since the impedances of the circuits tend to be small and the distances between them sufficiently large; A much bigger problem is the inductive coupling between the buses through which the power currents flow and the circuits through which the signal passes. If such a coupling occurs between the circuits of the same channel, it manifests itself in the form of distortion and can lead to significant non-linearity in the amplifier's characteristics. If this interaction extends to another (non-speech) channel, it will appear as crosstalk of the distorted signal. In any case, such a connection is highly undesirable and special measures must be taken to prevent its occurrence.

PCB routing is only one element of this battle, since the crosstalk must somehow not only be emitted, but also be received somewhere. Typically, the source of maximum radiation will be the internal electrical wires due to their overall length and abundance, the wire routing pattern will probably be the most critical to achieving the best performance, so various clamps, cable clamps, etc. will need to be used to secure them. The receiving device is most often the input circuits and feedback circuits, which are also located on the printed circuit board. For good operation of the device, it is necessary to study these issues from the point of view of maximum protection from radiation.

Distortion caused by power supply interference

The power rails of a Class B power amplifier carry very large and highly distorted currents. As already emphasized earlier, if due to induction their interaction is allowed on the circuit through which the acoustic signal passes, then the level of distortion will increase sharply. This applies to the PCB conductors and similarly to the cable connections, the sad truth is that it is quite easy to make an amplifier PCB that is absolutely perfect in every way except for this one requirement, and the only solution is to use a second fees. However, to obtain optimal results, the following requirements should be followed:

1. It is necessary to minimize electromagnetic radiation from the power rails by placing the positive and negative voltage rails as close to each other as physically possible. They should be located as far as possible from the input circuits of the amplifier stage and the connecting output terminals; The best method is to connect the power bus wires to the output stage on one side, and the rest of the amplifier wires on the other. Then you need to run wires from the output to power the rest of the amplifier; half-wave current will no longer pass through them, so it will not cause problems.
2. It is necessary to minimize the absorption of electromagnetic radiation from the power buses by minimizing the area of ​​​​the circuits covered by the input and feedback circuit wires. They form closed loops through the ground, so the area of ​​the loops covered by them should be minimal. Quite often, the best result can be obtained by maximizing the spatial separation and routing the input and feedback loop wires across the LF ground path, which runs through the center of the printed circuit board from the input to the output ground loop point. Inductive distortion can also occur when interacting with output wires and output ground wires. The latter case presents a rather serious problem, since it is usually difficult to change its position in space without updating the printed circuit board itself.

Installing Output Semiconductors

The most important fundamental decision is whether to install high-power output devices on the amplifier's main circuit board. There are a number of strong arguments in favor of such a decision, but, nevertheless, such a choice is not always the best.

Advantages:

1. The amplifier's printed circuit board can be designed to form a complete unit that can be thoroughly tested before it is installed in the chassis. This approach greatly facilitates testing, since access to various points of the circuit is provided from all sides; it also eliminates the possibility of surface damage to the PCB itself (scratches, etc.) during inspection.
2. There is no possibility of incorrect connection of output semiconductor devices, provided that the required semiconductor devices are installed in the correct positions. This is a fairly significant argument, since such errors usually disable the output semiconductor devices, and also lead to other negative effects that develop like falling dominoes, and which will require a large amount of time (and money) to correct.
3. All connecting wires leading to the output semiconductor devices should be as short as possible. This helps increase the stability of the output stage and resist the occurrence of RF oscillations.

Flaws:

1. If the amplifier's output devices require frequent replacement (which clearly indicates some very serious defect), then the repeated soldering operation will damage the traces of the printed circuit board. However, if the worst happens, the damaged section can always be replaced with a short conductor, so there is no need to scrap the printed circuit board; rest assured, such a repair option is always possible.
2. It is possible that the output semiconductor devices can become very hot, even when they are operating at nominal conditions; For TO3 type devices, a housing temperature of 90 °C is not unusual. If the mounting method used does not allow for some degree of resilience, thermal expansion may result in mechanical forces that can tear off the PCB mounting gaskets.
3. The heat sink will usually have significant dimensions and weight. Therefore, it is necessary to use a fairly rigid structure that secures the printed circuit board and radiator. Otherwise, the entire structure, due to the lack of sufficient rigidity, will vibrate during transportation, creating excessive forces in the places where the joints are soldered.

Making a good power amplifier has always been one of the difficult stages when designing audio equipment. Sound quality, softness of bass and clear sound of mid and high frequencies, detail of musical instruments - all these are empty words without a high-quality low-frequency power amplifier.

Preface

Of the variety of homemade low-frequency amplifiers on transistors and integrated circuits that I made, the circuit on the driver chip performed best of all. TDA7250 + KT825, KT827.

In this article I will tell you how to make an amplifier amplifier circuit that is perfect for use in homemade audio equipment.

Amplifier parameters, a few words about TDA7293

The main criteria by which the ULF circuit was selected for the Phoenix-P400 amplifier:

• Power approximately 100W per channel at 4 Ohm load;
• Power supply: bipolar 2 x 35V (up to 40V);
• Low input impedance;
• Small dimensions;
• High reliability;
• Speed ​​of production;
• High sound quality;
• Low noise level;
• Low cost.

This is not a simple combination of requirements. First I tried the option based on the TDA7293 chip, but it turned out that this was not what I needed, and here’s why...

Over all this time, I had the opportunity to assemble and test different ULF circuits - transistor ones from books and publications of Radio magazine, on various microcircuits...

I would like to say my word about the TDA7293 / TDA7294, because a lot has been written about it on the Internet, and more than once I have seen that the opinion of one person contradicts the opinion of another. Having assembled several clones of an amplifier using these microcircuits, I made some conclusions for myself.

The microcircuits are really quite good, although a lot depends on the successful layout of the printed circuit board (especially the ground lines), good power supply and the quality of the wiring elements.

What immediately pleased me about it was the fairly large power delivered to the load. As for a single-chip integrated amplifier, the low-frequency output power is very good; I would also like to note the very low noise level in the no-signal mode. It is important to take care of good active cooling of the chip, since the chip operates in “boiler” mode.

What I didn’t like about the 7293 amplifier was the low reliability of the microcircuit: out of several purchased microcircuits, at various points of sale, only two were left working! I burned one out by overloading the input, 2 burned out immediately when turned on (it seems like a factory defect), another one burned out for some reason when I turned it on again for the 3rd time, although before that it worked normally and no anomalies were observed... Maybe I was just unlucky.

And now, the main reason why I did not want to use modules based on TDA7293 in my project is the “metallic” sound that is noticeable to my ears, there is no softness and richness in it, the mid frequencies are a little dull.

I concluded that this chip is perfect for subwoofers or low-frequency amplifiers that will drone in the trunk of a car or at discos!

I will not touch on the topic of single-chip power amplifiers further; we need something more reliable and of high quality so that it is not so expensive in terms of experiments and errors. Assembling 4 channels of an amplifier using transistors is a good option, but it is quite cumbersome in execution, and it can also be difficult to configure.

So what should you use to assemble if not transistors or integrated circuits? - on both, skillfully combining them! We will assemble a power amplifier using a TDA7250 driver chip with powerful composite Darlington transistors at the output.

LF power amplifier circuit based on TDA7250 chip

Chip TDA7250 in a DIP-20 package is a reliable stereo driver for Darlington transistors (high-gain composite transistors), on the basis of which you can build a high-quality two-channel stereo UMZCH.

The output power of such an amplifier can reach or even exceed 100 W per channel with a load resistance of 4 Ohms; it depends on the type of transistors used and the supply voltage of the circuit.

After assembling a copy of such an amplifier and the first tests, I was pleasantly surprised by the sound quality, power and how the music produced by this microcircuit “came to life” in combination with transistors KT825, KT827. Very small details began to be heard in the compositions, the instruments sounded rich and “light”.

You can burn this chip in several ways:

• Reversing the polarity of power lines;
• Exceeding the maximum permissible supply voltage ±45V;
• Input overload;
• High static voltage.

Rice. 1. TDA7250 microcircuit in a DIP-20 package, appearance.

Datasheet for the TDA7250 chip - (135 KB).

Just in case, I purchased 4 microcircuits at once, each of which has 2 amplification channels. The microcircuits were purchased from an online store at a price of approximately $2 per piece. At the market they wanted more than $5 for such a chip!

The scheme according to which my version was assembled does not differ much from the one shown in the datasheet:

Rice. 2. Circuit of a stereo low-frequency amplifier based on the TDA7250 microcircuit and transistors KT825, KT827.

For this UMZCH circuit, a homemade bipolar power supply of +/- 36V was assembled, with capacitances of 20,000 μF in each arm (+Vs and -Vs).

Power Amplifier Parts

I’ll tell you more about the features of the amplifier parts. List of radio components for circuit assembly:

Name	Quantity, pcs	Note
TDA7250	1
KT825	2
KT827	2
1.5 kOhm	2
390 Ohm	4
33 Ohm	4	power 0.5W
0.15 ohm	4	power 5W
22 kOhm	3
560 Ohm	2
100 kOhm	3
12 ohm	2	power 1W
10 ohm	2	power 0.5W
2.7 kOhm	2
100 Ohm	1
10 kOhm	1
100 µF	4	electrolytic
2.2 µF	2	mica or film
2.2 µF	1	electrolytic
2.2 nF	2
1 µF	2	mica or film
22 µF	2	electrolytic
100 pF	2
100 nF	2
150 pF	8
4.7 µF	2	electrolytic
0.1 µF	2	mica or film
30 pf	2

The inductor coils at the output of the UMZCH are wound on a frame with a diameter of 10 mm and contain 40 turns of enameled copper wire with a diameter of 0.8-1 mm in two layers (20 turns per layer). To prevent the coils from falling apart, they can be fastened with fusible silicone or glue.

Capacitors C22, C23, C4, C3, C1, C2 must be designed for a voltage of 63V, the remaining electrolytes - for a voltage of 25V or more. Input capacitors C6 and C5 are non-polar, film or mica.

Resistors R16-R19 must be designed for a power of at least 5Watt. In my case, miniature cement resistors were used.

Resistances R20-R23, as well as R.L. can be installed with a power of 0.5W. Resistors Rx - power of at least 1W. All other resistances in the circuit can be set to a power of 0.25W.

It is better to select pairs of transistors KT827 + KT825 with the closest parameters, for example:

1. KT827A(Uke=100V, h21E>750, Pk=125W) + KT825G(Uke=70V, h21E>750, Pk=125W);
2. KT827B(Uke=80V, h21E>750, Pk=125W) + KT825B(Uke=60V, h21E>750, Pk=160W);
3. KT827V(Uke=60V, h21E>750, Pk=125W) + KT825B(Uke=60V, h21E>750, Pk=160W);
4. KT827V(Uke=60V, h21E>750, Pk=125W) + KT825G(Uke=70V, h21E>750, Pk=125W).

Depending on the letter at the end of the marking for KT827 transistors, only the voltages Uke and Ube change, the rest of the parameters are identical. But KT825 transistors with different letter suffixes already differ in many parameters.

Rice. 3. Pinout of powerful transistors KT825, KT827 and TIP142, TIP147.

It is advisable to check the transistors used in the amplifier circuit for serviceability. Darlington transistors KT825, KT827, TIP142, TIP147 and others with a high gain contain two transistors, a couple of resistances and a diode inside, so a regular test with a multimeter may not be enough here.

To test each of the transistors, you can assemble a simple circuit with an LED:

Rice. 4. Scheme for testing transistors of the P-N-P and N-P-N structure for operability in the key mode.

In each of the circuits, when the button is pressed, the LED should light up. Power can be taken from +5V to +12V.

Rice. 5. An example of testing the performance of the KT825 transistor, P-N-P structure.

Each pair of output transistors must be installed on radiators, since already at an average ULF output power their heating will be quite noticeable.

The datasheet for the TDA7250 chip shows the recommended pairs of transistors and the power that can be extracted using them in this amplifier:

At 4 ohm load
ULF power	30 W	+50 W	+90 W	+130 W
Transistors	BDW93, BDW94A	BDW93, BDW94B	BDV64, BDV65B	MJ11013, MJ11014
Housings	TO-220	TO-220	SOT-93	TO-204 (TO-3)
At 8 ohm load
ULF power	15 W	+30 W	+50 W	+70 W
Transistors	BDX53 BDX54A	BDX53 BDX54B	BDW93, BDW94B	TIP142, TIP147
Housings	TO-220	TO-220	TO-220	TO-247

Mounting transistors KT825, KT827 (TO-3 housing)

Particular attention should be paid to the installation of output transistors. A collector is connected to the housing of transistors KT827, KT825, so if the housings of two transistors in one channel are accidentally or intentionally shorted, you will get a short circuit in the power supply!

Rice. 6. Transistors KT827 and KT825 are prepared for installation on radiators.

If the transistors are planned to be mounted on one common radiator, then their cases must be insulated from the radiator through mica gaskets, having previously coated them on both sides with thermal paste to improve heat transfer.

Rice. 7. Radiators that I used for transistors KT827 and KT825.

In order not to describe for a long time how to install isolated transistors on radiators, I will give a simple drawing that shows everything in detail:

Rice. 8. Insulated mounting of transistors KT825 and KT827 on radiators.

Printed circuit board

Now I'll tell you about the printed circuit board. It will not be difficult to separate it, since the circuit is almost completely symmetrical for each channel. You need to try to distance the input and output circuits from each other as much as possible - this will prevent self-excitation, a lot of interference, and protect you from unnecessary problems.

Fiberglass can be taken with a thickness of 1 to 2 millimeters; in principle, the board does not need special strength. After etching the tracks, you need to tin them well with solder and rosin (or flux), do not ignore this step - it is very important!

I laid out the tracks for the printed circuit board manually, on a sheet of checkered paper using a simple pencil. This is what I have been doing since the times when one could only dream about SprintLayout and LUT technology. Here is a scanned stencil of the printed circuit board design for the ULF:

Rice. 9. Printed circuit board of the amplifier and the location of the components on it (click to open full size).

Capacitors C21, C3, C20, C4 are not on the hand-drawn board, they are needed to filter the power supply voltage, I installed them in the power supply itself.

UPD: Thank you Alexandru for PCB layout in Sprint Layout!

Rice. 10. Printed circuit board for UMZCH on the TDA7250 chip.

In one of my articles I told how to make this printed circuit board using the LUT method.

Download the printed circuit board from Alexander in *.lay(Sprint Layout) format - (71 KB).

UPD. Here are other printed circuit boards mentioned in the comments to the publication:

As for the connecting wires for power supply and at the output of the UMZCH circuit, they should be as short as possible and with a cross-section of at least 1.5 mm. In this case, the shorter the length and greater the thickness of the conductors, the less current loss and interference in the power amplification circuit.

The result was 4 amplification channels on two small scarves:

Rice. 11. Photos of finished UMZCH boards for four channels of power amplification.

Setting up the amplifier

A correctly assembled circuit made from serviceable parts begins to work immediately. Before connecting the structure to the power source, you need to carefully inspect the printed circuit board for any short circuits, and also remove excess rosin using a piece of cotton wool soaked in a solvent.

I recommend connecting speaker systems to the circuit when you first turn it on and during experiments using resistors with a resistance of 300-400 Ohms, this will save the speakers from damage if something goes wrong.

It is advisable to connect a volume control to the input - one dual variable resistor or two separately. Before turning on the UMZCH, we put the switch of the resistor(s) in the left extreme position, as in the diagram (minimum volume), then by connecting the signal source to the UMZCH and applying power to the circuit, you can smoothly increase the volume, observing how the assembled amplifier behaves.

Rice. 12. Schematic representation of connecting variable resistors as volume controls for ULF.

Variable resistors can be used with any resistance from 47 KOhm to 200 KOhm. When using two variable resistors, it is desirable that their resistances be the same.

So, let's check the performance of the amplifier at low volume. If everything is fine with the circuit, then the fuses on the power lines can be replaced with more powerful ones (2-3 Amperes); additional protection during operation of the UMZCH will not hurt.

The quiescent current of the output transistors can be measured by connecting an ammeter or multimeter in current measurement mode (10-20A) to the collector gap of each transistor. The amplifier inputs must be connected to common ground (complete absence of input signal), and speakers must be connected to the amplifier outputs.

Rice. 13. Circuit diagram for connecting an ammeter to measure the quiescent current of the output transistors of an audio power amplifier.

The quiescent current of the transistors in my UMZCH using KT825+KT827 is approximately 100mA (0.1A).

Power fuses can also be replaced with powerful incandescent lamps. If one of the amplifier channels behaves inappropriately (hum, noise, overheating of transistors), then it is possible that the problem lies in the long conductors going to the transistors; try reducing the length of these conductors.

In conclusion

That's all for now, in the following articles I'll tell you how to make a power supply for an amplifier, output power indicators, protection circuits for speaker systems, about the case and front panel...

If you need to make a simple but quite powerful UMZCH, the TDA2040 or TDA2050 microcircuit will be the best and inexpensive solution. This small stereo AF amplifier is built on the basis of two well-known TDA2030A microcircuits. Compared to the classic connection, this circuit has improved power filtering and optimized PCB layout. After adding any preamp and power supply, the design is ideal for making a homemade home audio power amplifier, approximately 15 W (each channel). The project is based on the TDA2030A, but you can use the TDA2040 or TDA2050, thereby increasing the output power by one and a half times. The amplifier is suitable for speakers with an impedance of 8 or 4 ohms. The advantage of the design is that it does not require bipolar power supply, like most. The circuit has good parameters, ease of startup and reliable operation.

Schematic diagram of the ULF

Amplifier 2x15W TDA2030 - stereo circuit

TDA2030A allows you to solder a class AB low-frequency amplifier. The microcircuit provides a large output current, while being characterized by low signal distortion. There is built-in short circuit protection, which automatically limits the power to a safe value, as well as thermal protection traditional for such devices. The circuit consists of two identical channels, the operation of one of which is described below.

Operating principle of the amplifier on TDA2030

Resistors R1 (100k), R2 (100k) and R3 (100k) serve to create a virtual zero for amplifier U1 (TDA2030A), and capacitor C1 (22uF/35V) filters this voltage. Capacitor C2 (2.2 uF/35V) cuts off the DC component - it prevents DC voltage from entering the input of the amplifier microcircuit through the linear input.

Elements R4 (4.7k), R5 (100k) and C4 (2.2 uF/35V) operate in a negative feedback loop and have the task of forming the frequency response of the amplifier. Resistors R4 and R5 determine the gain level, while C4 provides unity gain for the DC component.

Resistor R6 (1R) together with capacitor C6 (100nF) work in a system that forms the frequency response characteristic at the output. Capacitor C7 (2200uF/35V) prevents DC current from passing through the speaker (passing the AC audio signal of the music).

Diodes D1 and D2 prevent dangerous reverse polarity voltages from occurring in the speaker coil and damaging the chip. Capacitors C3 (100nF) and C5 (1000uF/35V) filter the supply voltage.

ULF printed circuit board

Printed circuit board ULF TDA2030

You can see the printed circuit board in the photographs. with drawings can be in the archive (without registration). As for assembly, it’s convenient to first solder two jumpers on the power buses. If possible, you should use a thicker wire, rather than a thin resistor leg, as is often the case. If the amplifier will operate with 8 Ohm speakers, and not 4 Ohms, capacitors C7 and C14 (2200uF/35V) can have a value of 1000uF.

You should definitely screw radiators or one common radiator onto the flanges, remembering that the housings of the TDA2030A microcircuits are internally connected to ground.

You can successfully use TDA2040 or TDA2050 microcircuits on a printed circuit board without any pinout changes. The board was designed so that it could be cut if necessary at the location indicated by the dotted line, and only one half of the amplifier with the U1 chip could be used. In place of connectors AR2 (TB2-5) and AR3 (TB2-5), you can solder wires directly if the audio connectors are fixed to the amplifier body.

Amplifier printed circuit board ready with parts arrangement

Case and power supply

Take a power supply either with a transformer plus a rectifier, or a ready-made switching one, for example from a laptop. The amplifier must be powered with an unstabilized voltage within the range of 12 - 30 V. The maximum supply voltage is 35 V, which is naturally better not to reach by a couple of volts, you never know.

Making a case from scratch is very troublesome, so the easiest way is to choose a ready-made box (metal, plastic) or even a ready-made case from an electronic device (satellite TV tuner, DVD player).

Evgenia Smirnova

To send light into the depths of the human heart - this is the purpose of the artist

Connecting speakers to a laptop, TV, or other music source sometimes requires amplification of the signal using a separate device. The idea of ​​building your own amplifier is a good one if you are inclined to work with printed circuit boards at home and have some technical skills.

How to make a sound amplifier

The beginning of work on assembling an amplification device for speakers of one type or another consists of searching for tools and components. The amplifier circuit is assembled on a printed circuit board using a soldering iron on a heat-resistant support. It is recommended to use special soldering stations. If you assemble it yourself for the purpose of testing the circuit or for use for a short period of time, the “on wires” option is suitable, but you will need more space to place the components. The printed circuit board guarantees the compactness of the device and ease of further use.

A cheap and widespread amplifier for headphones or small speakers is created on the basis of a microcircuit - a miniature control unit with a pre-wired set of commands for controlling an electrical signal. All that remains to be added to the circuit with the microcircuit is a few resistors and capacitors. The total cost of an amateur-grade amplifier is ultimately significantly lower than the price of ready-made professional equipment from the nearest store, but the functionality is limited to changing the output volume of the audio signal.

Remember the features of compact single-channel amplifiers that you assemble yourself based on TDA series microcircuits and their analogues. The microcircuit generates a large amount of heat during operation, so you should eliminate or minimize its contact with other parts of the device. A radiator grille for heat removal is recommended for use. Depending on the model of the microcircuit and the power of the amplifier, the size of the required heatsink increases. If the amplifier is assembled in a housing, you should first plan a place for the heat sink.

Another feature of assembling a sound amplifier with your own hands is the low voltage consumption. This allows you to use a simple amplifier in cars (powered by a car battery), on the road or at home (powered by a special unit or batteries). Some simplified audio amplifiers require a voltage of only 3 Volts. Power consumption depends on the degree of audio signal amplification required. The sound amplifier from the player for standard headphones consumes about 3 Watts.

It is recommended that a novice radio amateur use a computer program to create and view circuit diagrams. Files for such programs can have a *.lay extension - they are created and edited in the popular virtual tool Sprint Layout. Creating a circuit with your own hands from scratch makes sense if you have already gained experience and want to experiment with the knowledge you have gained. Otherwise, look for and download ready-made files that can be used to quickly assemble a replacement for a low-frequency amplifier for a car radio or a digital combo amplifier for a guitar.

For laptop

A do-it-yourself sound amplifier for a laptop is assembled in one of two cases: the built-in speakers are out of order, or their volume and sound quality are not enough for your needs. You will need a simple amplifier designed for a power of external speakers up to 2 Watts, and a winding resistance of up to 4 Ohms. To assemble it yourself, in addition to standard amateur radio tools (pliers, soldering station), you will need a printed circuit board, a TDA 7231 microcircuit, and a 9-volt power supply. Select your own housing to house the amplifier components.

Add the following items to the list of purchased components:

• non-polar capacitor 0.1 µF – 2 pcs.;
• polar capacitor 100 µF – 1 pc.;
• polar capacitor 220 µF – 1 pc.;
• polar capacitor 470 µF – 1 pc.;
• constant resistor 10 KOhm – 1 pc.;
• constant resistor 4.7 Ohm – 1 pc.;
• two-position switch – 1 pc.;
• jack for loudspeaker output – 1 pc.

Determine the assembly order yourself depending on which *.lay electrical diagram you downloaded. Select a radiator of such a size that its thermal conductivity allows you to maintain the operating temperature of the microcircuit below 50 degrees Celsius. If the device is constantly used outdoors with a laptop, it will need a homemade case with slots or holes for air circulation. You can assemble such a case with your own hands from a plastic container or the remains of old radio equipment, securing the board with long screws.

For DIY headphones

The simplest stereo amplifier for portable headphones should have low power, but the most important parameter will be power consumption. In an ideal example, the design is powered by AA batteries or, in extreme cases, by a simple 3-volt adapter. You will need a high-quality TDA 2822 microcircuit or its analogue (for example, KA 2209), an electronic circuit for assembling an amplifier with your own hands using a TDA 2822. Additionally, take the following components:

• capacitors 100 µF (4 pcs.);
• up to 30 cm of copper wire;
• socket for headphone cable.

A heat sink element will be needed if you want to make the amplifier compact and with a closed housing. The amplifier can be assembled on a ready-made or home-made printed circuit board or by surface mounting. The pulse transformer in the power supply may cause interference, so do not use it in this amplifier. The finished amplifier will provide pleasant and powerful sound from the player (record or radio signal), tablet or phone.

Subwoofer amplifier circuit

The low-frequency amplifier is assembled with your own hands on the TDA 7294 microcircuit. It is used both to create powerful acoustics with bass in the apartment, and as a car amplifier - in this case, however, you need to purchase a bipolar power supply of 30-35 Volts. The figures below describe the location of components, as well as the values ​​of resistors and capacitors. This subwoofer amplifier will provide an output power of up to 100 watts with outstanding low frequencies.

Mini sound amplifier for speakers

The design described above for laptops is suitable as a sound amplification device for domestic or foreign home speakers. Stationary placement of the device will allow you to choose any power adapter from those available. You can ensure the miniature size and acceptable appearance of an inexpensive amplifier by following several rules:

1. Ready-made high-quality printed circuit board.
2. Durable plastic or metal case (order from a specialist).
3. The placement of components is pre-planned.
4. The amplifier is soldered neatly, without unnecessary drops of solder.
5. The heatsink only touches the chip.
6. Ready-made sockets are used for signal output and power input.

DIY tube sound amplifier

Tube sound amplifiers are expensive devices, provided that you purchase all the components at your own expense. Old radio amateurs sometimes keep collections of tubes and other parts. Assembling a tube amplifier at home with your own hands is relatively easy if you are willing to spend a few days searching for detailed circuit diagrams on the Internet. The sound amplifier circuit in each case is unique and depends on the sound source (old tape recorder, modern digital equipment), power source, expected dimensions and other parameters.

Transistor sound amplifier

Assembling a sound preamplifier with your own hands without using complex microcircuits is possible using transistors. An amplifier based on germanium transistors can be easily integrated into modern audio systems; it does not require additional configuration. The disadvantage of transistor circuits is the larger size of the board assembly. The dependence on the “purity” of the background is also unpleasant - you will need a shielded cable, or an additional circuit for suppressing noise and ripple from the network.

Video: DIY audio power amplifier

Found an error in the text? Select it, press Ctrl + Enter and we will fix everything!